1. Field of the Invention
The present invention generally relates to the art of multi-user, on-demand video entertainment systems, and more specifically to a video server system including independent, concurrently operating remote data retrieval controllers for accessing video files from a central storage.
2. Description of the Related Art
User-on-demand, also known as pay-per-view, video entertainment systems are becoming increasingly popular in motel and hotel facilities as well as in larger scale community cable television (CATV) systems.
Such a system includes a video server located at a central location that stores a plurality of movies that can be selected for viewing by one or more users at any desired time. The video server is connected to television receivers at the individual user locations by a cable or other network.
Each user is provided with means for requesting that a selected movie be retrieved from the server and shown on his television receiver. In a small scale system such as installed in a motel or hotel, an interactive remote control unit can be provided for each television receiver by which the user can request a movie using a menu system displayed on the television screen. In a large scale system such as a community cable television network, the user can call the cable company by telephone to request that the movie fed to his home receiver.
A prior art video server system 10 is illustrated in FIG. 1, and comprises a mass storage unit in the form of a Redundant Array of Inexpensive Drives (RAID) disk drive array 12. Data access to and from the individual drives of the RAID array 12 is controlled by a master controller 14.
A plurality of movies are stored on the array 12 in a distributed or "striped" manner such that any movie can be viewed by more than one user, or even by all users simultaneously starting at different times. The RAID arrangement is further advantageous in that it balances the usage load over the disk drives.
The basic RAID configuration, including a description of distributed storage of data, is disclosed in U.S. Pat. No. 4,870,643, entitled "PARALLEL DRIVE ARRAY STORAGE SYSTEM", issued Sept. 26, 1989 to David Bultman et al, and an improved arrangement is disclosed in my prior U.S. Pat. No. 5,191,584, entitled "MASS STORAGE ARRAY WITH EFFICIENT PARITY CALCULATION", issued Mar. 2, 1993. Both of these patents are assigned to the Micropolis Corporation of Chatsworth, Calif., the assignee of the present invention.
In the illustrated prior art configuration, all of the video and audio movie data and control functions are processed by a PC server 16, which is typically a conventional personal computer (PC). A television receiver at the location of each user 18 is provided with an interactive remote control unit 20 by which the user can request a particular movie from a displayed menu on a pay-per-view basis. Movie requests from the remote control units 20 are sent to the PC server 16.
In response to a movie request, the server 16 sends a command to the RAID array 12 to retrieve the data corresponding to the requested movie from the disk drives. The data is read out of the array 12 and fed back through the server 16 to a decoder array 36 which converts the data into an audio/visual channel and feeds it to the requesting user 18. In order to enable more than one user to view a movie simultaneously, data is retrieved from the array 12 in small time multiplexed blocks.
The prior art system of FIG. 1 is adequate for applications including only a few users. However, a data rate of approximately 375 kilobytes/second per user is required to provide substantially real-time viewing. The data throughput rate scales in proportion to the number of users. A typical personal class computer is capable of a data rate of approximately 6 megabytes. Thus, the system 10 as illustrated in FIG. 1 is only capable of serving approximately 16 users 18.